In the production of custom thermoformed articles or parts, such as parts produced by blow molding, vacuum molding, rotomolding, compression molding, resin transfer molding and reaction injection molding, it is usually necessary to perform one or more secondary operations on each part after it is formed. For example, the part may require peripheral trimming on a computer numerically controlled (CNC) router machine having a high speed router which is automatically moved around the base of the part to trim off an outwardly projecting flange. Commonly, each part is supported during the secondary trimming operation by a corresponding vacuum router fixture which receives the part and has small vacuum passages extending from an internal vacuum chamber within the fixture for positively holding the part firmly against the fixture. Each router fixture must be precisely positioned on the bed or table of the CNC router machine and then attached with clamps and/or bolts, after which the fixture is connected to a vacuum or suction line. These set up operations for the router fixture for each part require substantial time, and when it is necessary to perform trimming on a number of different thermoformed parts, several hours may be required for interchanging router fixtures and for precisely locating and positively securing or clamping each fixture to the router table. During this time period, the router machine is not operating, and the operator of the machine is not producing.
The present invention is directed to an improved quick change tooling system for a vacuum holding fixture which receives a thermoformed part in order to perform a secondary operation on the part, such as a peripheral trimming operation. The tooling system of the invention provides for quickly removing a vacuum holding fixture for a part from a machine which performs a secondary operation on the part and for quickly attaching another vacuum holding fixture for another part to the machine. As a result, down time of the machine and nonproductive time of the machine operator are minimized during set up for each fixture. The quick change tooling system of the invention further provides for quickly positioning each vacuum holding fixture on the machine and for positively locking the fixture to the base of the machine in a precise predetermined position, thus eliminating the use of hand tools, bolts, clamps and other fastening means. The tooling system also provides for quickly removing the vacuum holding fixture from the machine.
In accordance with one embodiment of the invention, an attachment plate is secured to the bottom surface of a vacuum holding fixture for a thermoformed part and has an opening which connects with a vacuum chamber within the fixture. The fixture is provided with an array of small vacuum passages connecting the internal vacuum chamber with the outer surfaces of the fixture. The attachment plate is adapted to seat on the top wall of a vacuum box which is connected by a line to a vacuum source. A resilient annular seal is mounted on the top wall of the vacuum box around a vacuum opening and forms an airtight seal between the vacuum opening in the attachment plate and the aligned vacuum opening within the top wall of the vacuum box.
A plurality or three air actuated locking couplers positively secure the fixture attachment plate to the vacuum box and precisely locate the vacuum fixture relative to the vacuum box which is secured to the bed or table of a machine. Preferably, each of the locking couplers includes a knob or stud projecting downwardly from the attachment plate and having an enlarged head portion which is received within a locking cylinder recessed within the top wall of the vacuum box. Each locking cylinder has circumferentially spaced balls for engaging the head portion of the corresponding coupler stud, and a spring loaded piston surrounds the balls and normally holds the balls in a locking position. The balls of all couplers retract to released positions in response to pressurized air simultaneously acting on the pistons of the couplers.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.